Featured Science Paper

Seasonal variations of gravity wave activity in the lower stratosphere over an Antarctic Peninsula station

Gravity waves are buoyancy waves in the atmosphere. They can be produced from a variety of sources, e.g. wind flowing over mountains or large weather systems. When they break they deposit their energy and momentum, driving the circulation and temperature patterns in the atmosphere. In order to accurately reproduce their effects in atmospheric climate models, we need to observe gravity waves (and identify their sources). This is especially important for the Antarctic Peninsula region. Satellite data shows that there is a ‘hotspot’ of gravity wave activity in the stratosphere over the Antarctic Peninsula region — which has been thought to be mainly due to wind flow over the mountains. This paper examines the sources of gravity wave activity in the lower stratosphere (15km to 22km) above the Antarctic Peninsula using balloons launched from Rothera.

The paper uses eight years of data from radiosonde observations from Rothera. We primarily use radiosondes for meteorological observations measuring a range of atmospheric parameters such as temperature, wind speed and direction. They are launched on large weather balloons and record data as the balloons rise and continue to do so until the balloon pops (which can be up to 30km altitude). At Rothera there is one balloon launch a day, four times a week.

Using the data from 965 radiosonde launches our paper examined the seasonal variation in gravity wave energy and also the vertical propagation direction of the waves. What we showed was that the seasonal variation in gravity wave energy was due to different gravity wave sources dominating over the course of a year. Due to effects lower down in the atmosphere, the waves generated by the wind flow over the mountains only dominated for part of the year. The contribution from downward propagating waves, generated by the breakup of the polar vortex, also varied over the course of the year. This has shown that the seasonal variation in gravity wave activity over Rothera is not determined solely by those waves from wind flow over mountains but that downward propagating waves have an important contribution too.